The genesis of the subject invention resides in a continuing effort to improve extant EAS tags (also called EAS labels) and tag production practices such as are set forth in various commonly-assigned prior art patents, for example, U.S. Pat. No. 5,006,856.
Tags of the '856 patent comprise spiral coils disposed in generally facing relationship on opposed sides of a dielectric layer, with the coils interconnected in an area outside of the dielectric layer. A resonant circuit is accordingly provided and is enclosed within electrically insulative outer covering members.
In use, a tag is attached to an article to be monitored as against fraudulent activity, and if the article is carried to an exit of the surveillance zone, such as the exit of a store, an alarm condition attends incidence of energy on the tag of frequency equal to the resonant frequency of the tag.
Tags having facility for "deactivation" are likewise shown in the '856 patent and discussed also in detail below. The deactivation structure may comprise an electrically conductive member astride the turns of one of the spiral coils and isolated therefrom by an intervening layer of material which is normally electrically insulative but, on incidence of high energy on the tag, i.e., in excess of that required for causing alarming resonance, converts to electrically conductive character. On that event, the conductive member with the converted layer short-circuits the spiral coil. The deactivation normally precludes the tag from again resonating and typically takes place at a checkout counter, from which the article with tag therewith can freely pass from the surveillance zone.
As has been recognized in the past, electrostatic charge buildup on individual tags can cause undesirable tag deactivation by effecting conversion of the convertable layer. Such charge buildup can occur in the course of tag production and further in the course of printing on the tags. As is discussed also in detail below, tags are produced in a continuous sequence, with the deactivator structure applied continuously in the sequence, i.e., as a deactivator web providing electrical connection of the series of tags in the course of being produced. While the continuous deactivator web can function as a drain to prevent static discharge from deactivating the labels during the manufacturing process, it can also function as a vehicle for electrostatic charge to flow across a sequence of tags causing deactivation of the tag sequence in the course of production.
One past measure taken for avoiding such flow of electrostatic charge has been to make cuts through the deactivator web, as in FIG. 31 of the '856 patent (cuts 520). While the deactivator web remains continuous between adjacent tags, the '856 patent notes the cuts to be effective in preventing premature deactivation due to electrostatic charge in the tag manufacturing equipment or subsequently in printing equipment.
Another measure in this respect has been to provide a conductive film for charge drain purposes, as is shown at 600, 601 in FIG. 31 of commonly-assigned prior art U.S. Pat. No. 4,910,499. The conductive film constitutes a component of the tags following production and serves to drain charge also in the course of printing. Its presence, however, prevents accurate determination of the "Q" of the tag. Further, the drain mechanism is fully capacitive, given that an insulative web intervenes the conductive film and the tag coil structure.
A further measure in this respect is seen in FIGS. 25 and 26 of the '856 patent, where, at the completion of forming a sequence of connected tags, holes 407 are punched through the deactivation layer between adjacent tags to sever the same and render adjacent tags with no electrical connection therebetween. This practice affords electrical isolation of adjacent completed and connected tags when they are collected on a reel. However, this measure affords no relief as against electrostatic charge which may build up in the preceding steps in the manufacture of the tags. Further, since the holes are punched on completion of tag making, they extend fully through all layers of the tag and are undesirably viewable in the finished product.
From applicant's viewpoint, the various past efforts to overcome the adverse influence of electrostatic charge buildup in/on deactivatable EAS tags/circuits, while constituting meaningful steps in the evolution of correction of the problem and providing effective production practice and effective tags, have not yielded as low a reject rate in production as is optimally desirable.
To provide more specific background discussion facilitating an appreciation of the practices and tags of the subject invention, detailed description of extant practices is now provided, with reference to those drawings herein which are labelled as being prior art.
Referring to FIG. 1, there is shown an exploded view of a tag generally indicated at 19. The tag 19 is shown to include a sheet 20T having pressure sensitive adhesive 21 and 22 on opposite faces thereof. A mask 23 in a spiral pattern covers a portion of the adhesive 21 and a release sheet 24T is releasably adhered to the adhesive 22. The mask 23 renders the adhesive 21 which it covers non-tacky or substantially so.
A conductor spiral indicated generally at 25 includes a spiral conductor 26 having a number of turns. The conductor 26 is of substantially the same width throughout its length except for a connector bar 27 at the outer end portion of the conductor spiral 26. There is a sheet of dielectric 28T over and adhered to the conductor spiral 25 and the underlying sheet 20T by means of adhesive 29.
A conductor spiral generally indicated at 30 includes a spiral conductor 31 having a number of turns. The conductor 31 is adhered to adhesive 29' on the dielectric 28T. The conductor 31 is substantially the same width throughout its length except for a connector bar 32 at the outer end portion of conductor spiral 30.
The conductor spirals 25 and 30 are generally aligned in face-to-face relationship except for portions 33 which are not face-to-face with the conductor 26 and except for portions 35 which are not face-to-face with the conductor 31. A sheet 37T has a coating of a pressure sensitive adhesive 38 masked off in a spiral pattern 39. The exposed adhesive 38' is aligned with the conductor spiral 30. Adhesive is shown in FIG. 1 by heavy stippling and the masking is shown in FIG. 1 by light stippling with cross-hatching.
The connector bars 27 and 32 are electrically connected, as for example by staking 90 (FIG. 2). The staking 90 occurs where connector bars 27 and 32 are separated only by adhesive 29 or are in direct electrically conductive contact with no intervening adhesive or other medium. There is no paper, film or the like between the connector bars 27 and 32. Accordingly, the staking 90 is effective for electrically conductive interconnection of connector bars 27 and 32.
The process for making the tag of FIG. 1, which does not include deactivation structure, is described in FIG. 3 of the '856 patent, to which patent incorporating reference is hereby made for all purposes.
On the other hand, FIG. 3 herein shows that portion of the '856 FIG. 3 manufacturing apparatus as modified to provide tags with deactivation structure. A pair of coating and drying stations is generally indicated at 111 and 112 where respective coatings 113 and 114 in the form of continuous stripes are printed and dried. The coating 113 is conductive and is applied directly onto the pressure sensitive adhesive 38 on the web 37. The coatings 114 are wider than the respective coatings 113 which they cover to assure electrical isolation, as best shown in FIGS. 4 and 5. The coatings 114 are composed of a normally non-conductive activatable material.
Referring to FIGS. 6 and 7, there is shown a finished deactivatable tag 37T' with the coatings 113 and 114 having been severed as the tag 37T' is severed from the tag web as indicated at 113T and 114T respectively. As shown the coating 113T is of constant width and thickness throughout its length and the coating 114T is of constant width and thickness but is wider than the coating 113T. The coating 113T which is conductive is thus electrically isolated from the conductor spiral 30. The coatings 113T and 114T comprise an activatable connection AC (FIG. 9) which can be activated by subjecting the tag to a high level of energy above that for causing the resonant circuit to be detected at an interrogation zone.
The showings of prior art practices in FIGS. 8 and 9 herein correspond to FIGS. 24 and 25 of the '856 patent. The deactivator webs 318 and 319, corresponding to the deactivator structure 113T and 114T of FIGS. 6 and 7 hereof, are separated into longitudinally spaced deactivator strips or stripes 318' and 319'. The separation is accomplished in accordance with the specific embodiment shown in FIG. 8, by punching out portions of the web 238 and the deactivator webs 318 and 319 to provide holes 407. For this purpose, a diagrammatically illustrated rotary punch 403 and a rotary die 404 are used. The rotary punch 403 has punches 405 and the rotary die 404 has cooperating die holes 406. The resultant holes 407 are narrower than the spacing between the resonant circuits. The holes 407 are thus registered with the margins of the longitudinally spaced resonant circuits as shown in FIG. 9. Thus, the probability of arcing of static electricity between resonant circuits in a longitudinal direction and between deactivator strips 318' (or 319') is lessened. However, such "severing" of the deactivation webs takes place at a quite late stage in the manufacturing process and does not preclude electrostatic charge movement in preceding manufacturing process steps.
FIGS. 10 and 11 herein correspond respectively with FIGS. 31 and 32 of the '856 patent. In FIG. 10, resonant circuits RC formed of connected pairs of spiral conductors 400 and 401 having plural turns are shown provided with an activatable connection or deactivator AC. The deactivators AC are made from a deactivator web ACW. In the manufacture of the tag web shown in FIG. 10, the deactivator web ACW is cut as shown at 520. Each cut 520 is more than a slit because it causes permanent spacing or separation between portions or sections or strips AC1, AC2 and AC3 associated with each tag T. As shown, each tag T comprises the portion of the tag web between adjacent pairs of phantom lines TL. The section AC1 extends between one end of the tag T along one phantom line TL and a cut 520, the section AC2 extends between adjacent but spaced cuts 520 of a tag T, and the section AC3 extends between the other cut 520 in the tag T and the other end of the tag T along the other phantom line TL.
Such cutting or slitting is practiced at a quite early stage of the manufacturing process since the deactivator web must be exposed to perform the cutting.
FIG. 11 shows the upper spiral conductor 401. The deactivator web ACW is comprised of normally non-conductive or breakdown material 521. The deactivator web ACW is also comprised of a deactivating conductor in the form of a vacuum metalized coating 522 of aluminum to which the normally nonconductive breakdown material 521 is adhered. The coating or layer 522 is deposited on a polyester film 523 which acts as a carrier or support for the coating 522 and the breakdown material 521.
A mask pattern 524 (corresponding to mask pattern 23) is disposed between the film 523 and an adhesive coating 525 on a polyester film 526. The cuts 520 are identical and one of the cuts 520 is shown in detail in FIG. 11. The cut 520 in FIG. 11 is shown to have two widths for a reason as will be evident from FIG. 12.
The upper spiral conductor 401 has eight conductor portions 401-1 through 401-8 at first through eighth locations numbered 1 through 8. In the preferred embodiment, one cut 520 is spaced between the first and second conductor portions 401-1 and 401-2, that is, between the first and second locations and another cut 520 is spaced between the seventh and eighth conductor portions 401-7 and 401-8 between the seventh and eighth locations. The adjacent cuts 520 of any one tag effectively make section AC2 the deactivator AC. It is evident that the deactivator AC is adjacent and crosses less than all the turns of the spiral conductor 401. When the deactivator AC is operated, the breakdown coating 521 at one or more locations 2 through 7 becomes conductive and consequently the deactivating conductor 522 becomes electrically connected to the resonant circuit at the location or locations 2 through 7 where breakdown occurs. If there is breakdown at only one location, the conductor 522 acts like a spur electrically connected to the spiral conductor 401 and thus affects the resonant circuit. However, breakdown can also occur at two or more locations, second through seventh, which will electrically connect portions of the spiral conductor 401 to each other to prevent detection of the resonant circuit of the tag.
The '856 patent states that there is even considerable improvement in deactivation when a cut 520 is made through the deactivator web ACW only between the first and second conductor portions 401-1 and 401-2 or only between the seventh and eighth conductor portions 401-7 and 401-8. In this case there is only one cut 520 in the deactivator web in each tag. Accordingly, the deactivator strip in each tag is separated into two deactivator sections or deactivator strips.
The short deactivation strips, AC1 and AC3 across TL in FIG. 10, however, provide electrical continuity between successive circuits until the severing of the deactivator web occurs, as noted at a quite late stage of the manufacturing process.
Referring to FIG. 12, there is diagrammatically illustrated a portion of the process for making the tags shown in FIGS. 10 and 11. Cutter roll 529 has cutter blades 530 which produce the cuts 520 in the deactivator web ACW. The web 37 passes between the cutter roll 529 and a back-up roll 531. It should be borne in mind that the web 37 is under tension as it is drawn partially about rolls 67 and 116, heated drum 115 and roll 117. The deactivator web has been cut into sections AC1, AC2 and AC3, which are no longer in tension and therefore are free to shrink. The deactivator sections AC1, AC2 and AC3 are not under tension and consequently they do not stretch along with the web 37. Specifically, with reference to FIG. 11, the resulting cut opening 527 in the polyester film 526 the associated adhesive 525 and pattern 524 are narrower than the cut opening 528 in the deactivator AC and its associated supporting or carrier web 523. Further, it is found that the gap provided by cuts 520, clearly less than that afforded by holes 407 (FIG. 9), is not of sufficient measure to effectively insure preclusion of movement of electrostatic charge. Also, the practices of cutting can themselves give rise to electrostatic charge. Finally, it has been found that for the cut tag version, higher deactivation field intensity is required and that, with the tag retaining a partly non-deactivated coil, i.e., that located outwardly of cuts 520, the deactivated tag can, at times, still resonate as if it were not deactivated.
While the cuts 520 also have the effect of preventing premature deactivation in the tag manufacturing equipment or subsequently in printing equipment due to electrostatic charge, applicant looks to the same, as in the case of the first described approach to the electrostatic charge problem (holes 407 above) as not providing as low a reject rate in production as is optimally desirable.
To summarize the state of the art, present practices call for cutting the deactivator web at a quite early stage of the process, since the deactivator web need be exposed for cutting. This undermines the effectiveness of the deactivator web in any subsequent static drain function. The continuous film drain provided in dielectric coupling with the coil structures is limited in that the charge drain is fully capacitive. Further, in present practices, the severing of the deactivator web takes place at a final stage of the process, and such step thus does not afford benefit in electrically separating adjacent tags during manufacture up to such final stage. Also, the step provides a hole extending fully through the tag which, to certain users, is aesthetically undesired.